package com.github.yangyishe.p100;

import java.util.Arrays;

/**
 * 36. 有效的数独
 * https://leetcode.cn/problems/valid-sudoku/?envType=study-plan-v2&envId=top-interview-150
 *
 * 请你判断一个 9 x 9 的数独是否有效。只需要 根据以下规则 ，验证已经填入的数字是否有效即可。
 *
 * 数字 1-9 在每一行只能出现一次。
 * 数字 1-9 在每一列只能出现一次。
 * 数字 1-9 在每一个以粗实线分隔的 3x3 宫内只能出现一次。（请参考示例图）
 *
 *
 * 注意：
 *
 * 一个有效的数独（部分已被填充）不一定是可解的。
 * 只需要根据以上规则，验证已经填入的数字是否有效即可。
 * 空白格用 '.' 表示。
 *
 *
 * 示例 1：
 *
 *
 * 输入：board =
 * [["5","3",".",".","7",".",".",".","."]
 * ,["6",".",".","1","9","5",".",".","."]
 * ,[".","9","8",".",".",".",".","6","."]
 * ,["8",".",".",".","6",".",".",".","3"]
 * ,["4",".",".","8",".","3",".",".","1"]
 * ,["7",".",".",".","2",".",".",".","6"]
 * ,[".","6",".",".",".",".","2","8","."]
 * ,[".",".",".","4","1","9",".",".","5"]
 * ,[".",".",".",".","8",".",".","7","9"]]
 * 输出：true
 * 示例 2：
 *
 * 输入：board =
 * [["8","3",".",".","7",".",".",".","."]
 * ,["6",".",".","1","9","5",".",".","."]
 * ,[".","9","8",".",".",".",".","6","."]
 * ,["8",".",".",".","6",".",".",".","3"]
 * ,["4",".",".","8",".","3",".",".","1"]
 * ,["7",".",".",".","2",".",".",".","6"]
 * ,[".","6",".",".",".",".","2","8","."]
 * ,[".",".",".","4","1","9",".",".","5"]
 * ,[".",".",".",".","8",".",".","7","9"]]
 * 输出：false
 * 解释：除了第一行的第一个数字从 5 改为 8 以外，空格内其他数字均与 示例1 相同。 但由于位于左上角的 3x3 宫内有两个 8 存在, 因此这个数独是无效的。
 *
 *
 * 提示：
 *
 * board.length == 9
 * board[i].length == 9
 * board[i][j] 是一位数字（1-9）或者 '.'
 */
public class Problem36 {
    public static void main(String[] args) {
        String[][] board1=new String[][]{
                {"8","3",".",".","7",".",".",".","."}
,{"6",".",".","1","9","5",".",".","."}
,{".","9","8",".",".",".",".","6","."}
,{"8",".",".",".","6",".",".",".","3"}
,{"4",".",".","8",".","3",".",".","1"}
,{"7",".",".",".","2",".",".",".","6"}
,{".","6",".",".",".",".","2","8","."}
,{".",".",".","4","1","9",".",".","5"}
,{".",".",".",".","8",".",".","7","9"}
        };
        char[][] board=new char[9][9];
        for(int i=0;i<9;i++){
            for(int j=0;j<9;j++){
                board[i][j]=board1[i][j].charAt(0);
            }
        }


        Problem36 problem36 = new Problem36();
        boolean validSudoku = problem36.isValidSudoku(board);
        System.out.println(validSudoku);
    }

    /**
     * 思路
     * 逐个遍历行, 列, 3*3单元格, 以类hash表记录的方式, 记录有无重复的值
     * 有则提前返回false
     * 无则最后返回true
     * @param board
     * @return
     */
    public boolean isValidSudoku(char[][] board) {
        int maxSize=9;
        int[] numHash=new int[maxSize];

        // 行遍历
        for(int i=0;i<maxSize;i++){
            Arrays.fill(numHash,0);
            for(int j=0;j<maxSize;j++){
                if(board[i][j]=='.'){
                    continue;
                }
                if(numHash[board[i][j]-'1']==0){
                    numHash[board[i][j]-'1']=1;
                }else{
                    return false;
                }
            }
        }

        // 列遍历
        for(int i=0;i<maxSize;i++){
            Arrays.fill(numHash,0);
            for(int j=0;j<maxSize;j++){
                if(board[j][i]=='.'){
                    continue;
                }
                if(numHash[board[j][i]-'1']==0){
                    numHash[board[j][i]-'1']=1;
                }else{
                    return false;
                }
            }
        }

        // 3*3小单元遍历
        for(int i=0;i<maxSize;i+=3){
            for(int j=0;j<maxSize;j+=3){
                Arrays.fill(numHash,0);
                for(int m=0;m<3;m++){
                    for(int n=0;n<3;n++){
                        int rowIndex=i+m;
                        int colIndex=j+n;
                        if(board[rowIndex][colIndex]=='.'){
                            continue;
                        }
                        if(numHash[board[rowIndex][colIndex]-'1']==0){
                            numHash[board[rowIndex][colIndex]-'1']=1;
                        }else{
                            return false;
                        }
                    }
                }
            }
        }


        return true;
    }
}
